Tuesday, July 9, 2013

New paper finds another non-hockey-stick in Arctic Siberia

A new paper published in Palaeogeography, Palaeoclimatology, Palaeoecology reconstructs temperatures in Arctic Siberia over the past 15,000 years and finds another non-hockey-stick with temperatures ~2C higher than the present during the early to mid Holocene [9,000 to 4,000 years ago].

Graph at left side shows temperature variations over the past 15,000 years, temperatures ~2C higher than the present during the early to mid Holocene.

Highlights

We evaluate a pollen-climate transfer function at the tundra-taiga transition.

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Mean July temperature and annual precipitation can be inferred.

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A Holocene reconstruction from the Siberian Arctic was evaluated.

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We discuss the power and limits of our transfer function.

Abstract

This study aims to establish, evaluate, and apply a modern pollen-climate transfer function from the transition zone between arctic tundra and light-needled taiga in Arctic Siberia. Lacustrine samples (n=96) from the northern Siberian lowlands of Yakutia were collected along four north-to-south transects crossing the arctic forest line. Samples span a broad temperature and precipitation gradient (mean July temperature, TJuly: 7.5–18.7 °C; mean annual precipitation, Pann: 114–315 mm/yr). Redundancy analyses are used to examine the relationship between the modern pollen signal and corresponding vegetation types and climate. Performance of transfer functions for TJuly and Pann were cross-validated and tested for spatial autocorrelation effects. The root mean square errors of prediction are 1.67 °C for TJuly and 40 mm/yr for Pann. A climate reconstruction based on fossil pollen spectra from a Siberian Arctic lake sediment core spanning the Holocene yielded cold conditions for the Late Glacial (1–2 °C below present TJuly). Warm and moist conditions were reconstructed for the early to mid Holocene (2 °C higher TJuly than present), and climate conditions similar to modern ones were reconstructed for the last 4,000 years. In conclusion, our modern pollen data set fills the gap of existing regional calibration sets with regard to the underrepresented Siberian tundra-taiga transition zone. The Holocene climate reconstruction indicates that the temperature deviation from modern values was only moderate despite the assumed Arctic sensitivity to present climate change.